This disclosure relates generally to the field of image processing, and more particularly to a system and a method for selecting, on a per material and per scene basis, hyperspectral wavebands that are useful for detecting target materials in scenes, and cueing multispectral imaging of the scenes with the useful wavebands.
Detection of smaller, dimmer targets in cluttered scenes using spectral sensors is typically limited by the sensors' ground sample distance (GSD) and ground resolved distance (GRD), to some extent. In conventional hyperspectral imaging (HSI) systems, HSI sensors collect typically 200-400 narrow spectral bands over a given regime (e.g., VNIR/SWIR, LWIR), and routinely use fast focal lengths (e.g., approximately F/3) to provide a balance of signal to noise ratio (SNR) and ground sample distance (GSD), the latter being the dominant term in estimating image quality of a sensor system on the National Imagery Interpretability Rating Scale (NIIRS). While existing HSI sensors are able to extract targets from cluttered imagery using spectral algorithms, they are generally limited to detection of targets having sizes 50-100% of the sensor GSD.
Multi-spectral imaging (MSI) sensors utilizing the same apertures as HSI sensors can offer higher SNR and much finer GSD (e.g., approximately F/12) spanning the same spectral range. However, MSI sensors typically image non-optimal spectral bands and poorly characterize the atmosphere in a scene, and are generally limited to detecting target sizes spanning several GSDs. For example, prior HSI systems generally employ wide spectral band coverage, due to uncertainty whether an appropriate spectral band, or bands, are being used for target detection. Such systems produce panchromatic images, which have less energy per spectral channel, than images produced by MSI sensors.
Imaging systems are typically designed with a tradeoff between the spectral resolution (i.e., the range of wavelengths that are sampled by an imaging detector) and the spatial resolution. Commercial satellites, such as IKONOS and GeoEye, commonly provide three or more relatively coarse resolution MSI bands along with a finer spatial resolution panchromatic band. Panchromatic sharpening, wherein fine spatial resolution panchromatic imagery is merged with higher spectral but lower spatial resolution multispectral imagery to create a single high-resolution color image, is used in some satellite imaging systems. However, such techniques are computationally burdensome, and are not directed to improving resolution or target detection capability.
Thus, there exists a need for methods and systems for enhanced, efficient detection and identification of targets using a single optical telescope imaging a cluttered scene, especially for applications involving long range air and/or space imaging.